Which of these statements about C o C N 6 3 - is true?

1. ${\left[\mathrm{C}\mathrm{o}{\left(\mathrm{C}\mathrm{N}\right)}_6\right]}^{3-}$ has no unpaired electrons and will be in a low-spin configuration.
2. ${\left[\mathrm{C}\mathrm{o}{\left(\mathrm{C}\mathrm{N}\right)}_6\right]}^{3-}$ has four unpaired electrons and will be in a low-spin configuration.
3. ${\left[\mathrm{C}\mathrm{o}{\left(\mathrm{C}\mathrm{N}\right)}_6\right]}^{3-}$ has four unpaired electrons and will be in a high-spin configuration.
4. ${\left[\mathrm{C}\mathrm{o}{\left(\mathrm{C}\mathrm{N}\right)}_6\right]}^{3-}$ has no unpaired electrons and will be in a high-spin configuration.

Solution

Due to strong Ligand field of $\mathrm{C}{\mathrm{N}}^{-}$ ions pairing of electrons takes place in inner 3d orbital it is a low spin complex with no unpaired electrons.

Asked in: NEET 2015 (Phase 1)

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